This invention relates to an abrasive for use in oral compositions such as dentrifrices, prophylactic pastes and the like. More particularly, this invention relates to a highly cleaning, low abrading abrasive for use in oral compositions which consists of calcium hydrogenphosphate anhydride (secondary calcium phosphate anhydride) whose crystallite has an average size of 300 to 3,500 angstroms as measured by X-ray diffractometry. This invention also relates to an oral composition containing the abrasive.
In general, abrasives for use in oral compositions, for example, dentifrices and prophylactic pastes are required to have an increased ability of efficiently removing away stain, dental plaque, and food debris adhered to or deposited on teeth with the aid of physical action, that is, an improved cleanability as a tooth cleaning agent, and to exhibit mild abrasiveness to such an extent that the tooth enamel will not be damaged, as well as to prevent deposition of dental plaque and calculus.
In this case, the efficiency of physical removal of stain, plaque, and food debris can be increased by using an abrasive having increased abrasiveness. Particularly, it has been a common practice in the prior art to enhance the cleaning effect of an abrasive on the tooth surface by increasing the abrasiveness thereof. However, increasing abrasiveness is generally opposite to the prevention of damage to the tooth surface. The higher the abrasiveness, the greater is the likelihood that the tooth surface would be abraded away. Particularly when brushing is done inadequately, there is the increased likelihood that wedge-shaped deffects would be formed and the tooth surface would be marred or scratched and reduced in luster. Thus, there is a need for an abrasive for use in oral compositions which will not cause damage to the tooth surface while retaining a proper degree of abrasiveness and having improved cleaning effect.